1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Alpha Particles in a Vacuum

  1. Feb 17, 2014 #1
    As a radioactive sample decays in a glass vacuum container, and the released alpha particles collide with the glass, would it be correct to assume that the particles "bounce around?"
  2. jcsd
  3. Feb 18, 2014 #2
    They're likely to penetrate the glass and lose their energy along the way becoming helium atoms.
  4. Feb 18, 2014 #3

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper

    Pretty much what he said. For more detail see:

    If by "bounce around" you mean, off the walls of the container - no.
    Energetic alphas may scatter off the nuclei, some may back-scatter... but really you expect absorption.

    On the scale of the individual alpha, the glass is a kind of fog with hard points in it.

    Alpha particle tracks in a cloud chamber:

    ... illustrates the short range, with deflection/absorbtion by denser matter.
    Last edited by a moderator: Sep 25, 2014
  5. Feb 18, 2014 #4
    Thanks, just what I was looking for.

    So in a man made vacuum, it would be expected for some α-particles to be absorbed by the glass, while others would ionize into helium gas inside the chamber, correct?
    Last edited by a moderator: Sep 25, 2014
  6. Feb 19, 2014 #5
    They would deionize into helium atoms inside of the glass.
  7. Feb 20, 2014 #6

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper

    Alphas are the same as doubly-ionized helium atoms - different origin though.

    In a vacuum chamber there are, in principle, no electrons or anything for the alphas ot inetract with so: no, they would not ionize or deionize or anything before hitting the walls.

    When they interact with the atoms in the walls of the chamber - then they would lose kinetic energy and eventually deionize by picking up a couple of the electrons there.

    The picture I gave you was for alphas in a cloud chamber - i.e. not a vacuum.
  8. Feb 20, 2014 #7
    What do you mean by different origins?
    Where do you think helium comes from? (Assuming Earthly sources)
  9. Feb 20, 2014 #8
    And the helium would emerge outside of the chamber or be trapped inside the glass?
  10. Feb 20, 2014 #9
    The helium atom is deposited inside of the glass but won't necessarily stay there. Helium atoms have high mobility and will diffuse fairly fast. That's why helium balloons never last as long as you'd like them to :(
  11. Feb 20, 2014 #10
    Ok thanks, you guys have been very helpful.
  12. Feb 20, 2014 #11

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper

    Immediate origins. Perhaps you prefer "processes"?

    "Ionization" is commonly understood as a process rather than a state or configuration.
    i.e. http://www.britannica.com/EBchecked/topic/293007/ionization

    In this sense - doubly ionized helium atoms started out with all their electrons (having collected some along the way, and hung around in pockets underground for a while before being dug up, separated out, and bottled, and shipped to the lab or wherever) and then had them removed, while new alphas just emitted from nuclear decay have yet to acquire any electrons.

    That's what I mean by "different origins".

    Assuming Earthly sources, bearing in mind the above: It mainly comes out of holes in the ground, but I mostly get it from the gasses cupboard at the back of the lab.

    One day I saw a tech toting a cylinder of helium, and asked after the origin of that helium.
    The tech replied, "It came from the store room."
    I explained that this was incorrect, "Surely," said I, "This helium came from nuclear processes under the ground."
    The tech replied, "All I know is, it's heavy. If you want to lecture me, you can carry this *** cylinder."
    On hearing that, I was enlightened. ;)

    But, no worries aye, at least the answers were helpful.
    Have fun.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook